Gain flattened optical fiber amplifier

• US 6,339,494 B1
• Filed: 01/14/2000
• Issued: 01/15/2002
• Est. Priority Date: 01/14/1999
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd. (Samsung Group)
• Original Assignee: Samsung Electronics Co. Ltd. (Samsung Group)
• Inventors: Yoon, Soo-Young, Jung, Rae-Sung, Hwang, Seong-Teak
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US09/482,536
• Time in Patent Office: 732 Days
• Field of Search: 359/337.1, 359/341.33
• US Class Current: 359/337.1
• CPC Class Codes: H01S 2301/04 Gain spectral shaping, flattening
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/06758 Tandem amplifiers
• CPC Class Codes: H01S 3/094011 with bidirectional pumping, i.e. with injection of the pump light from both two ends of the fibre
• CPC Class Codes: H04B 10/2941 using an equalising unit, e.g. a filter H04B10/296 takes precedence
• CPC Class Codes: H04B 2210/003 Devices including multiple stages, e.g., multi-stage optical amplifiers or dispersion compensators

Abstract

An optical fiber amplifier capable of having a flattened gain irrespective of the intensity of an input signal light. The optical fiber amplifier includes a first amplifying unit for amplifying an input signal light using a first pumping light to obtain a predetermined gain, a second amplifying unit for re-amplifying the signal light amplified by the first amplifying unit, using a second pumping light, to obtain the same gain as the predetermined gain, and a pumping light separating unit for allowing the amplified signal light outputted from the first amplifying unit to enter the second amplifying unit while preventing the first pumping light from reaching the second amplifying unit and preventing the second pumping light from reaching the first amplifying unit, whereby the amplified signal light entering the second amplifying unit is allowed to be amplified only by the second pumping light.

Claims

1. An optical fiber amplifier comprising:

a first amplifying unit for amplifying an input signal light using a first pumping light to obtain a predetermined gain;

a second amplifying unit for re-amplifying the signal light amplified by the first amplifying unit, using a second pumping light, to obtain the same gain as the predetermined gain; and

a pumping light reflection filter for allowing the amplified signal light outputted from the first amplifying unit to enter the second amplifying unit and totally reflecting both the first pumping light and preventing the second pumping light, whereby the first amplifying unit is allowed to be bidirectionally pumped only by the first pumping light and the second amplifying unit is allowed to be bidirectionally pumped only by the second pumping light.

2. The optical fiber amplifier according to claim 1, wherein the first amplifying unit comprises:

a pumping light source for generating the first pumping light;

a wavelength division multiplexer for combining the input signal light with the first pumping light; and

an erbium-doped optical fiber coupled to the wavelength division multiplexer and adapted to amplify the input signal light using the first pumping light.

3. The optical fiber amplifier according to claim 2, wherein the second amplifying unit comprises:

a second erbium-doped optical fiber coupled to the pumping light reflection filter and adapted to re-amplify the amplified signal light using the second pumping light;

a second wavelength division multiplexer for outputting the amplified signal light from the second erbium-doped optical fiber while inputting the second pumping light to the second erbium-doped optical fiber; and

a second pumping light source for generating the second pumping light and supplying the generated second pumping light to the second wavelength division multiplexer.

4. The optical fiber amplifier according to claim 3, wherein the pumping light reflection filter is spaced apart from the first erbium-doped optical fiber by a distance corresponding to 10 to 90% of the distance from the first erbium-doped optical fiber to the second erbium-doped optical fiber.

5. An optical fiber amplifier comprising:

a first amplifying unit responsive to a first pumping light for amplifying an input signal light to obtain a first amplified signal light having predetermined gain;

a pumping light reflection filter for separating the first pumping light from said first amplified signal light by totally reflecting said first pumping light back to said first amplifying unit to again be used to amplify said input signal light, and outputting said first amplified signal light having said first pumping light removed therefrom; and

a second amplifying unit responsive to a second pumping light for amplifying said first amplified signal light output from said pumping light reflection filter to obtain the an output amplified signal light having said predetermined gain, wherein said pumping light reflection filter prevents said second pumping light from being applied to said first amplifying unit by totally reflecting said second pumping light back to said second amplifying unit to again be used to amplify said first amplified signal light.

6. The optical fiber amplifier according to claim 5, wherein the first amplifying unit comprises:

a pumping light source for generating the first pumping light;

a wavelength division multiplexer for combining the input signal light with the first pumping light; and

an erbium-doped optical fiber, coupled to an output of said wavelength division multiplexer, for amplifying the input signal light in response to the first pumping light.

7. The optical fiber amplifier according to claim 5, wherein the second amplifying unit comprises:

an erbium-doped optical fiber coupled to an output of said pumping light reflection filter for amplifying the first amplified signal light in response to said second pumping light;

a pumping light source for generating the second pumping light; and

a wavelength division multiplexer for providing said second pumping light to said erbium-doped optical fiber and outputting said output amplified signal light having said predetermined gain.

8. The optical fiber amplifier according to claim 7, wherein the pumping light reflection filter is spaced apart from the first erbium-doped optical fiber by a distance corresponding to 10 to 90% of the distance from the first erbium-doped optical fiber to the second erbium-doped optical fiber.

9. An optical fiber amplification method comprising the steps of:

amplifying, in response to a first pumping light at a first amplifying unit, an input signal light to obtain a first amplified signal light having predetermined gain;

reflecting, in totality, the first pumping light from said first amplified signal light and outputting said first amplified signal light having said first pumping light removed therefrom;

amplifying, in response to a second pumping light at a second amplifying unit, said first amplified signal light output by said reflecting step to obtain the an output amplified signal light having said predetermined gain; and

reflecting, in totality, said second pumping light to prevent said second pumping light from being applied to said first amplifying unit.

10. The method as set forth in claim 9, wherein said step of amplifying said input signal light comprises the steps of:

generating the first pumping light;

combining, in a wavelength division multiplexer, the input signal light with the first pumping light; and

exciting ions of erbium in an erbium-doped optical fiber coupled to an output of said wavelength division multiplexer, with both the generated and the reflected first pumping light to amplify said input signal light.

11. The method as set forth in claim 10, wherein said step of reflecting the first pumping light comprises a step of applying said first amplified signal light output from said erbium-doped optical fiber to a pumping light reflection filter.

12. The method as set forth in claim 11, wherein said step of amplifying said first amplified signal light comprises the steps of:

generating the second pumping light;

providing said second pumping light, via a second wavelength division multiplexer, to a second erbium-doped optical fiber coupled to an output of said pumping light reflection filter, said pumping light reflection filter performing said step of reflecting said second pumping light to prevent said second pumping light from being applied to said first erbium-doped optical fiber;

exciting ions of erbium in said second erbium-doped optical fiber, in response to both the generated and the reflected second pumping light, to amplify the first amplified signal light to produce said output amplified signal light having said predetermined gain, said output amplified signal light being output via a second wavelength division multiplexer.